1. Field of the Invention
The present invention relates to a total reflection X-ray fluorescence apparatus used in a trace analysis of particles located near a surface such as surface contaminations by total reflection X-ray fluorescence.
2. Related Background Art
Total reflection X-ray fluorescence will be briefly described below.
When X-rays are radiated on an optically flat surface at a small glancing angle, the X-rays are reflected at the same angle as the glancing angle without being absorbed by a radiated material. In other words, the X-rays are totally reflected. In this case, if a specimen is placed on the surface by which the X-rays are totally reflected, since X-rays other than those radiated on the specimen are totally reflected, fluorescent X-rays emerging from the specimen can be detected in a state wherein scattered X-rays can be apparently ignored. Therefore, a spectral measurement with a high S/N ratio can be attained (Nippon Kinzoku Gakkai Kaiho, vol. 24, No. 11 (1985) pp. 956-961). Such an analysis method is called the total reflection X-ray fluorescence.
Qualitative/quantitative analysis of the specimen is performed based on the result of the spectral measurement. As analysis examples, for qualitative/quantitative analysis of a specimen placed on a wafer surface, "Progress in X-ray Analysis 19" (Agune Technical Center) pp. 217-226, Technical Reports of University of Electro-Communications, Osaka, "Natural Science Edition" 22 (1986), from p. 87, and the like are known, and for qualitative/quantitative analysis of a solution dripped on a wafer surface, "Progress in X-ray Analysis 19" (Agune Technical Center) pp. 237-249, and the like are known.
According to the prior art technique, it was difficult to make X-rays radiate at a small glancing angle to the optically flat surface on which a specimen is placed so as to meet conditions for total reflection of X-rays.
Also, if X-ray total reflection conditions are satisfied, X-rays enter to a depth of about 100 .ANG. of a surface portion of an optically flat surface. For this reason, X-rays detected by the above-mentioned total reflection X-ray fluorescence include fluorescent X-rays radiated from a base material having the optically flat surface, and X-rays unique to an X-ray source target (Mo, W, or the like) and continuous X-rays (white X-rays). Since those X-rays are detected as a background level of the analysis result, they induce an increase in detection lower-limit density of a small amount of an element placed as a specimen on the optically flat surface of the base material, and also induce a decrease in quantitative precision of the element.
Further, although the conventional total reflection X-ray fluorescence apparatus can designate an analysis position on a surface for totally reflecting X-rays, it cannot be discriminated by only analysis of the designated position whether the designated region can represent an attaching state of a particle on the entire surface for totally reflecting X-rays or corresponds to a region where a large amount of particles is locally present. For this reason, the surface for totally reflecting the X-rays is divided into a plurality of regions. The amount of particles cannot be determined unless analysis is independently performed for all the divided regions to confirm an attaching state of a particle, resulting in much time and poor work efficiency.